Heating-medium heating unit and vehicle air conditioner using the same

ABSTRACT

In a heating-medium heating unit equipped with a first heating-medium circulation box and a second heating-medium circulation box which are in close contact with both surfaces of a PTC heater, in which heating-medium circulation passages are formed in the interior, and which are joined to each other in a liquidtight manner, wherein joining surfaces are sealed with liquid gaskets, the heating-medium circulation passages are provided with joining-surface cooling channels that cool the joining surface which is sealed with a liquid gasket and on which the heat from the PTC heater acts. The joining-surface cooling channels are provided at positions closer to the joining surface than to the PTC heater.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 13/499,994filed on Apr. 3, 2012, which is a National Stage Application ofPCT/JP2011/058417 filed on Apr. 1, 2011, which is based on and claimsthe benefit of priority from Japanese Patent Application No.2010-093294, filed Apr. 14, 2010, which are hereby incorporated byreference in their entirety.

TECHNICAL FIELD

The present invention relates to a heating-medium heating unit thatheats a heating medium using a positive temperature coefficient (PTC)heater, and to a vehicle air conditioner using the same.

BACKGROUND ART

One known heating-medium heating unit for heating a medium to be heateduses a PTC heater that uses a positive temperature coefficientthermistor device (PTC device) as a heating element. The PTC heater hasa positive temperature thermistor coefficient and thus shows anincreasing value of resistance as the temperature increases, whichallows the current consumption to be controlled and the increase intemperature to be slowed, and thereafter, the current consumption andthe temperature of the heat generating portion reach a saturation regionand are stabilized; that is, the PTC heater has a self temperaturecontrol characteristic.

The PTC heater has the characteristic that the current consumption isreduced as the temperature of the heater increases, and thereafter whenthe temperature reaches a saturation region of a fixed temperature, thecurrent consumption stabilizes at a low value. The use of thischaracteristic provides advantages in that current consumption can bereduced and an abnormal increase in the temperature of the heatgenerating portion can be prevented.

Therefore, PTC heaters are used in many technical fields. Also in thefield of air conditioning, as disclosed in PTL 1, for example, in ahybrid-vehicle air conditioner, a heating-medium heating unit in whichthe PTC heater is applied to a heating unit for heating a heating medium(here, engine coolant) to be supplied to a radiator for heating air whenthe engine is stopped has been proposed.

In this heating-medium heating unit, two heating-medium circulationboxes are joined to each other via an O-ring in a liquidtight manner,and a flat PTC heater is closely interposed between the twoheating-medium circulation boxes. The heating-medium circulation boxesare each configured such that a plurality of box components are joinedvia O-rings in a liquidtight manner, and the heating-medium circulationboxes each have therein a circulation path through which engine coolant,which is a heating medium, circulates.

The heating-medium circulation boxes each have a flat radiating surfacein close contact with the PTC heater, and a grooved level-differenceportion is formed between the flat surface and a joining surface formedon the outer periphery of each heating-medium circulation box (boxcomponent) (see FIG. 5 in PTL 1).

This is for the purpose of preventing the O-rings from being overheatedby increasing the length of the heat transmission path from the PTCheater to the foregoing O-rings to prevent the O-rings interposedbetween the joining surfaces from deteriorating in quality due to highheat generated from the PTC heater, which would cause liquid leaks. Thelevel-difference portion is provided with wiring members extending fromthe PTC heater.

CITATION LIST Patent Literature

{PTL 1} Japanese Unexamined Patent Application, Publication No.2008-56044

SUMMARY OF INVENTION Technical Problem

However, since the heating-medium heating unit described in PTL 1 has aconfiguration in which a flat PTC heater is closely interposed between apair of heating-medium circulation boxes configured such that aplurality of box components are joined via O-rings in a liquidtightmanner, as described above, a large number of O-rings are needed, thusincreasing the number of components, and moreover, complicating theassembly work, and furthermore, needing the carving of fitting groovesin which the O-rings are fitted in the joining surfaces of the boxcomponents, which has caused an increase in the manufacturing cost ofthe heating-medium heating unit.

Furthermore, since level-difference portions, such as grooves, areformed between the radiating surfaces in close contact with the PTCheater and the joining surfaces formed on the outer peripheries of theheating-medium circulation boxes (box components), the number ofman-hours for machining the box components is large, which causes anincrease in the manufacturing cost of the heating-medium circulationboxes, and thus the entire heating-medium heating unit.

Furthermore, since wiring members extending from the PTC heater aredisposed between the PTC heater and the outer peripheries (joiningsurfaces) of the heating-medium circulation boxes, the dimensions of theouter peripheries of the heating-medium circulation boxes aresignificantly larger than the area of the flat surface of the PTCheater, which also causes an increase in the manufacturing cost of theheating-medium heating unit.

The present invention has been made in consideration of suchcircumstances, and an object thereof is to provide a heating-mediumheating unit which accommodates a PTC heater, in which the manufacturingcost of heating-medium circulation boxes through which a heating mediumcirculates is reduced, and in which leakage of the heating medium fromthe heating-medium circulation boxes is prevented so that thereliability can be enhanced, as well as a vehicle air conditioner usingthe same.

Solution to Problem

To achieve the above object, the present invention provides thefollowing solutions.

A heating-medium heating unit according to a first aspect of the presentinvention includes a flat PTC heater; a first heating-medium circulationbox in which a plurality of box components are stacked one on another,which is in close contact with one surface of the PTC heater, and inwhich a heating-medium circulation passage is formed in the interior;and a second heating-medium circulation box in which a plurality of boxcomponents are similarly stacked on one another, which is in closecontact with the other surface of the PTC heater, in which aheating-medium circulation passage is formed in the interior, and whichis joined to the first heating-medium circulation box in a liquidtightmanner, wherein a heating medium that circulates through theheating-medium circulation passages in the first and secondheating-medium circulation boxes is heated by heat radiated from bothsurfaces of the PTC heater, wherein at least one of a joining surfacebetween the box components that constitute the first heating-mediumcirculation box and the second heating-medium circulation box and ajoining surface between the first heating-medium circulation box and thesecond heating-medium circulation box is sealed with a liquid gasket;and wherein the heating-medium circulation passage of at least the firstheating-medium circulation box or the second heating-medium circulationbox is provided with a joining-surface cooling channel that is sealedwith the liquid gasket and that cools the joining surface on which theheat from the PTC heater acts.

With the heating-medium heating unit, the heating-medium heating unitcan be assembled by sealing spaces between the plurality of boxcomponents constituting the heating-medium heating unit using onlyliquid gaskets. The two heating-medium circulation boxes can also beassembled with the space therebetween being sealed using only a liquidgasket. This can therefore eliminate a large number of O-rings used inthe related art, thus reducing the number of components and assemblyman-hours, and moreover, can eliminate fitting grooves that areconventionally carved in the individual joining surfaces of the boxcomponents to fit the O-rings therein, thereby reducing the number ofman-hours for machining the box components, thus allowing themanufacturing cost of the heating-medium circulation boxes to bereduced.

Moreover, since the liquid gaskets applied to the joining surfaces canbe protected from the heat from the PTC heater by using the coolingchannel provided in the heating-medium circulation passage of at leastthe first heating-medium circulation box or the second heating-mediumcirculation box, the durability of the liquid gasket is enhanced, andthus leakage of the heating medium from the joining surface can beprevented.

In the heating-medium heating unit according to the first aspect of thepresent invention, preferably, the joining-surface cooling channel isprovided at a position closer to the joining surface sealed with theliquid gasket than to the PTC heater. This allows the liquid gasketapplied to the joining surface to be protected from the heat from thePTC heater more reliably.

In the heating-medium heating unit according to the first aspect of thepresent invention, preferably, the joining surface is provided with anoutside sealing section that seals a space between the heating-mediumcirculation passage and the outside and a board sealing section thatseals a space between the heating-medium circulation passage and aportion communicating with a portion accommodating a board forcontrolling the PTC heater, in which the width of the board sealingsection is larger than the width of the outside sealing section. Thiscan reliably prevent coolant leakage to the control board whileeliminating the O-ring so that the manufacturing cost can be reduced,thereby enhancing the reliability of the heating-medium heating unit.

In the heating-medium heating unit according to the first aspect of thepresent invention, preferably, a radiating surface of at least one ofthe first heating-medium circulation box and the second heating-mediumcirculation box, the radiating surface being in close contact with thePTC heater, and the joining surface between the first heating-mediumcirculation box and the second heating-medium circulation box are formedas a continuous flat surface without a level-difference. This canremarkably simplify machining of at least the first or secondheating-medium circulation box, thus reducing the manufacturing cost ofthe heating-medium circulation box.

Furthermore, in the heating-medium heating unit according to the firstaspect of the present invention, preferably, the PTC heater and thefirst and second heating-medium circulation boxes are formed in arectangular shape, and a wiring member of the PTC heater extends from anend of the PTC heater in the longitudinal direction. This can eliminatethe wiring members of the PTC heater interposed between the long side ofthe PTC heater and the long side of the heating-medium circulation box,and hence the outer peripheral dimensions of the heating-mediumcirculation box can be brought close to the planar outside dimensions ofthe PTC heater, and in addition, the heating-medium circulation box canbe made compact, and thus the manufacturing cost can be reduced.

In the heating-medium heating unit, preferably, PTC devices thatconstitute the PTC heater are disposed in a plurality of rows along thechannel direction of the heating-medium circulation passages, theplurality of PTC heaters have different widths, and ON/OFF states of thePTC devices can be individually controlled. With this configuration, thewiring members of the PTC heater can be easily provided together at oneend of the PTC heater in the longitudinal direction, the amount of heatfrom the PTC heater can be controlled with a simple configuration, andthus a reduction in the manufacturing cost due to the size reduction ofthe heating-medium heating unit and enhanced reliability can beachieved.

Furthermore, a vehicle air conditioner according to a second aspect ofthe present invention includes a blower that circulates outside air orvehicle interior air, a cooler provided downstream of the blower, and aradiator provided downstream of the cooler, wherein a heating mediumheated by the heating-medium heating unit according to the first aspectcan circulate through the radiator. This can enhance the reliabilitywhile reducing the manufacturing cost of the heating-medium heatingunit.

Advantageous Effects of Invention

Thus, with the heating-medium heating unit according to the presentinvention and the vehicle air conditioner using the same, it is possibleto reduce the manufacturing cost of the heating-medium circulation boxwhich accommodates a PTC heater and through which a heating mediumcirculates, and to prevent leakage of the heating medium from theheating-medium circulation box, and hence the reliability can beenhanced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of a vehicle air conditioneraccording to an embodiment of the present invention.

FIG. 2 is a perspective view of a heating-medium heating unit accordingto an embodiment of the present invention.

FIG. 3 is an exploded perspective view of the heating-medium heatingunit according to the embodiment of the present invention.

FIG. 4 is a vertical cross-sectional view taken along line IV-IV in FIG.2.

FIG. 5 is a vertical cross-sectional view taken along line V-V in FIG.2.

FIG. 6 is a perspective view of a board-accommodating box shown in FIG.3, turned upside down.

FIG. 7 is a bottom view of an upper heating-medium circulation box takenalong arrows VII-VII in FIG. 4.

FIG. 8 is a top view of a lower heating-medium circulation box takenalong arrows VIII-VIII in FIG. 4.

FIG. 9 is an enlarged diagram of part IX in FIG. 4.

DESCRIPTION OF EMBODIMENT

An embodiment of the present invention will be described hereinbelowusing FIGS. 1 to 9.

FIG. 1 shows a schematic configuration diagram of a vehicle airconditioner 1 according to this embodiment. The vehicle air conditioner1 is, for example, a hybrid-vehicle air conditioner and is equipped witha casing 3 forming an air channel 2 through which outside air or vehicleinterior air is taken in, controls the temperature thereof, and guidesit into the vehicle interior.

The casing 3 accommodates, in sequence from the upstream side to thedownstream side of the air channel 2, a blower 4 that takes in outsideair or vehicle interior air, increases the pressure thereof, and blowsit downstream; a cooler 5 that cools the air blown by the blower 4; aradiator 6 that heats the air cooled by passing through the cooler 5;and an air mix damper 7 that adjusts the ratio of the amount of airpassing through the radiator 6 to the amount of flowing air bypassingthe radiator 6 to control the temperature of the air mixed downstreamthereof.

The downstream side of the casing 3 is connected to a plurality of vents(not shown) through which the temperature-controlled air is blown outinto the vehicle interior via a blowing-mode switching damper and a duct(not shown). The cooler 5 constitutes a refrigerant circuit togetherwith a compressor, a condenser, and an expansion valve (not shown) andcools air passing therethrough by evaporating a refrigerant that isadiabatically expanded at the expansion valve.

The radiator 6 constitutes a heating-medium circulating circuit 11together with a tank 8, a pump 9, an engine (not shown), and aheating-medium heating unit 10 according to the present invention.Engine coolant of a hybrid vehicle is used as a heating medium flowingthrough the heating-medium circulating circuit 11. The heating-mediumcirculating circuit 11 heats the air passing through the radiator 6 inthe casing 3 by heating the engine coolant with the heating-mediumheating unit 10 when the temperature of the engine coolant, serving asthe heating medium, does not significantly increase, such as duringhybrid driving, and by circulating the heated engine coolant through theheating-medium circulating circuit 11 with the pump 9.

FIG. 2 shows a perspective view of the heating-medium heating unit 10;FIG. 3 shows an exploded perspective view of the heating-medium heatingunit 10; and FIGS. 4 and 5 show vertical cross-sectional views of theheating-medium heating unit 10.

The heating-medium heating unit 10 is equipped with a firstheating-medium circulation box A configured like a casing such that aplurality of box components 20, 21, and 30 are stacked one on another; asecond heating-medium circulation box B which is configured like acasing such that a plurality of box components 50 and 51 are similarlystacked one on another and which is joined to the lower surface of thefirst heating-medium circulation box A in a liquidtight manner; and aPTC heater 40 sandwiched between the first and second heating-mediumcirculation boxes A and B.

The first heating-medium circulation box A is formed such that therectangular board-accommodating box 20, to the upper surface of whichthe cap 21 is joined, and the upper heating-medium circulation box 30having the same rectangular shape as the board-accommodating box 20 arejoined together in a liquidtight manner. The second heating-mediumcirculation box B is formed of the lower heating-medium circulation box50 having the same rectangular shape as the upper heating-mediumcirculation box 30 and the cap 51, which is joined to the lower surfaceof the lower heating-medium circulation box 50 in a liquidtight manner.The first heating-medium circulation box A, the second heating-mediumcirculation box B, and the other box components 20, 21, 30, 50, and 51are tightened together with a plurality of bolts 58 to form a singleunit, as shown in FIG. 2 and FIG. 4.

The PTC heater 40 has a rectangular, flat shape smaller than those ofthe upper heating-medium circulation box 30 and the lower heating-mediumcirculation box 50, the upper surface of the PTC heater 40 is in closecontact with a flat radiating surface 38 formed at the lower surface ofthe upper heating-medium circulation box 30, and the lower surface ofthe PTC heater 40 is in close contact with a flat radiating surface 56formed on the upper surface of the lower heating-medium circulation box50, as will be described later in detail.

The board-accommodating box 20 is a rectangular half casing which isformed of a thermally conducting material, such as an aluminum alloy,whose upper surface is tightly sealed by the cap 21, and whose interiorserves as a board-accommodating space S, in which a control board 22(see FIGS. 3 and 4) that controls the PTC heater 40 is accommodated. Thecontrol board 22 incorporates heat generating components and controlcircuits, such as field effect transistors (FETs) 23, and is suppliedwith a high voltage of 300 V for driving the PTC heater 40 and a lowvoltage of 12 V for control.

The control board 22 is fixedly disposed on supporting portions 24projecting from the bottom surface of the board-accommodating box 20 bybeing fastened with screws 25 a at the four corners. The heat generatingcomponents, such as the FETs 23, are disposed on the lower surface sideof the control board 22 and are fastened and fixed with screws 25 b tothe upper surface of a cooling portion 26 provided on the bottom surfaceof the board-accommodating box 20 that is in contact therewith via aninsulating layer (not shown) therebetween. The heat generatingcomponents, such as the FETs 23, and the cooling portion 26 are disposedin the vicinity of the inlet of heating-medium circulation passages(circulation paths 33), described later, provided in the upperheating-medium circulation box 30, to enhance the cooling effect on theheat generating components.

Wire insertion holes 27 are formed at one end face of theboard-accommodating box 20 (see FIGS. 3 and 6), through which wiringmembers 40 a (see FIG. 2) connected to the control board 22 are passed.Wire routing holes 28 (see FIG. 6) through which a harness connectingthe control board 22 and the PTC heater 40 passes are formed in thelower surface at one end of the board-accommodating box 20. A harnessinsertion hole 29 (see FIG. 3) is formed at the other end of theboard-accommodating box 20, through which an electrical harness 22 a(see FIG. 2) connecting to the control board 22 passes.

FIGS. 3 to 5 and FIG. 7 illustrate the heating-medium circulationpassages in the upper heating-medium circulation box 30. The upperheating-medium circulation box 30 is a rectangular half casing which isformed of a thermally conducting material, such as an aluminum alloy,and whose upper surface is provided with a pair of inlet header 31 andoutlet header 32 formed at both ends and parallel grooved circulationpaths 33, which are formed between the inlet header 31 and the outletheader 32 and are separated by a large number of fins 33 a. The uppersurfaces of the inlet header 31, the outlet header 32, and thecirculation paths 33 are sealed off by the bottom surface of theboard-accommodating box 20 in a liquidtight manner (see FIGS. 4 and 5).

Thus, an engine-coolant circulation passage through which the enginecoolant flowing into the inlet header 31 is distributed to the largenumber of circulation paths 33 so as to flow simultaneously in parallelin the circulation paths 33 toward the outlet header 32 is formedbetween the board-accommodating box 20 and the upper heating-mediumcirculation box 30. The engine coolant flowing in the circulation paths33 does not flow directly into the outlet header 32 but flows into acirculation opening 35 (see FIG. 7), described later, formed in thelower surface of the upper heating-medium circulation box 30. Theabove-described cooling portion 26 formed on the bottom surface of theboard-accommodating box 20 is cooled by the engine coolant circulatingin the circulation paths 33, described above, and thus constitutes acooling structure for the control board 22.

The inlet header 31 is provided with an engine-coolant inflow portion34, and the outlet header 32 is provided with the circulation opening 35connecting to the lower heating-medium circulation box 50, a circulationopening 36 through which the engine coolant flowing from the lowerheating-medium circulation box 50 is made to flow outwards, as will bedescribed later, and an engine-coolant outflow portion 37 communicatingwith the outside via the circulation opening 36. The inflow portion 34and the outflow portion 37 are provided with respective union members 34a and 37 a (see FIGS. 2 and 5) that allow hose members constituting theheating-medium circulating circuit 11 to be connected thereto.

Furthermore, the lower surface of the upper heating-medium circulationbox 30 is provided with a wide depressed portion (see FIGS. 4, 5 and 7)whose ceiling surface serves as the flat radiating surface 38 that is inclose contact with the upper surface of the PTC heater 40. Thisdepressed portion faces the back surfaces of the circulation paths 33through which the engine coolant circulates and is formed such that thePTC heater 40 is fitted therein. Wire insertion holes 39 (see FIG. 3)are formed at the end of the upper surface of the upper heating-mediumcirculation box 30 opposite to the circulation openings 35 and 36, andthe wire insertion holes 39 match the wire routing holes 28 of theboard-accommodating box 20.

FIGS. 3 to 5 and FIG. 8 illustrate heating-medium circulation passagesin the lower heating-medium circulation box 50. The lower heating-mediumcirculation box 50 is a rectangular half casing which is constituted bya thermally conducting material, such as an aluminum alloy, in whichcommunication openings 52 and 53 (see FIG. 8) are provided at one endthereof, and the communication openings 52 and 53 match the circulationopenings 35 and 36 of the upper heating-medium circulation box 30,respectively.

The lower surface of the lower heating-medium circulation box 50 isprovided with parallel grooved circulation paths 54 that extend from thecommunication opening 52 toward the other end and that make a U-turn atthe other end to return to the communication opening 53 and that areseparated by a large number of fins 54 a (see FIG. 4). The supplychannels and the return channels of the U-shaped circulation paths 54are separated by a partition wall 54 b (see FIG. 4) higher than the fins54 a. The lower surfaces of the circulation paths 54 are tightly sealedby the cap 51, as described above, and the cap 51 has a U-shaped shallowdepressed portion 55 (see FIG. 3) that matches the shapes of thecirculation paths 54 and the partition wall 54 b.

Thus, a heating-medium circulation passage through which the enginecoolant flowing into the communication opening 52 is distributed fromthe communication opening 52 to the large number of circulation paths54, circulates in the individual circulation paths 54 simultaneously inparallel, and makes a U-turn at the other end to reach the communicationopening 53 is formed between the lower heating-medium circulation box 50and the cap 51.

The communication opening 52 of the lower heating-medium circulation box50 communicates with the circulation opening 35 provided in the outletheader 32 of the upper heating-medium circulation box 30 so that theengine coolant flowing in the circulation paths 33 of the upperheating-medium circulation box 30 flows therein. The communicationopening 53 of the lower heating-medium circulation box 50 communicateswith the circulation opening 36 provided in the outlet header 32 of theupper heating-medium circulation box 30 to constitute a passage throughwhich the engine coolant flowing in the lower heating-medium circulationbox 50 is made to flow outwards from the circulation opening 36 via theoutflow portion 37.

The upper surface of the lower heating-medium circulation box 50 servesas the radiating surface 56 (see FIGS. 3 to 5 and FIG. 8) and holds thePTC heater 40 with the flat radiating surface 38 at the lower surface ofthe upper heating-medium circulation box 30 therebetween like asandwich, so that the radiating surfaces 38 and 56 are inpressure-contact with compressive heat conducting layers 44, to bedescribed later, bonded to both surfaces of the PTC heater 40.

FIGS. 3 and 4 and FIGS. 7 to 9 illustrate the configuration of the PTCheater 40. The PTC heater 40 is rectangular in overall shape. The PTCheater 40 is constituted by PTC devices 41 a, 41 b, and 41 c serving asheat-generating elements, disposed in, for example, three rows, alongthe channel direction of the heating-medium circulation passages(circulation paths 33 and circulation paths 54). Of the three PTCdevices 41 a, 41 b, and 41 c, the PTC devices 41 a and 41 c at both endsare set to be, for example, twice as wide as the PTC device 41 b at thecenter.

As shown in an enlarged cross-sectional view in FIG. 9, the PTC devices41 a, 41 b, and 41 c each have a stacked structure in which electrodeplates 42, noncompressive insulating layers 43, and the compressive heatconducting layers 44 are stacked in sequence. The PTC devices 41 a, 41b, and 41 c are configured such that the ON/OFF states thereof can beindividually controlled by control circuits incorporated in the controlboard 22.

The electrode plates 42 are for supplying electric power to the PTCdevices 41 a, 41 b, and 41 c, are rectangular thin plates similar to thePTC devices 41 a, 41 b, and 41 c, and have electrical conductivity andthermal conductivity. The noncompressive insulating layers 43 arerectangular thin plates, are each constituted by an insulating material,such as a polyamide film, and have thermal conductivity. Thenoncompressive insulating layers 43 are 0.1 mm or less in thickness.This is for the purpose of minimizing the thermal resistance between thePTC devices 41 a, 41 b, and 41 c and the electrode plates 42 and betweenthe upper heating-medium circulation box 30 (radiating surface 56) andthe lower heating-medium circulation box 50 (radiating surface 38)provided at the outside thereof and for providing sufficient electricalinsulation.

Furthermore, the compressive heat conducting layers 44 are rectangularsheet members having compressibility, which are constituted byinsulating sheets, such as silicone sheets and have thermalconductivity. The compressive heat conducting layers 44 are, ifconstituted by silicone sheets, set to be about 0.4 mm to 2.0 mm inthickness to reduce the thermal resistance between the PTC device 41serving as a heat-generating element and the upper heating-mediumcirculation box 30 (radiating surface 38) and the lower heating-mediumcirculation box 50 (radiating surface 56). The thickness of at least 0.4mm or more ensures a compressing function, allowing the upperheating-medium circulation box 30 and the lower heating-mediumcirculation box 50 to be reliably brought into close contact with thePTC heater 40 by using the compressibility when the PTC heater 40 ismounted between the upper heating-medium circulation box 30 and thelower heating-medium circulation box 50, and allowing the mountingdimensional tolerance to be absorbed.

Thus, as shown in FIGS. 4 and 5, the PTC heater 40 can heat the enginecoolant circulating in the upper heating-medium circulation box 30 andthe lower heating-medium circulation box 50 provided in close contactwith both sides thereof by radiating the heat from both sides.

The PTC heater 40 has wiring members 40 b at one end thereof, and thewiring members 40 b are bent upwards at right angles to the planardirection of the PTC heater 40 and are inserted into the wire insertionholes 39 of the upper heating-medium circulation box 30 and the wireinsertion routing holes 28 of the board-accommodating box 20. The wiringmembers 40 b are guided to the control board 22, so that the cable-likewiring members 40 a (see FIG. 2) are drawn outwards from the controlboard 22 through the wire insertion holes 27 of the board-accommodatingbox 20, as described above. The wire insertion holes 27 are fitted witha waterproof, dustproof wire cap 40 c.

The heating-medium circulating circuit 11 is connected to the inflowportion 34 of the upper heating-medium circulation box 30.Low-temperature engine coolant pumped from the pump 9 flows through theinflow portion 34 into the inlet header 31 and is distributed to theindividual circulation paths 33 (see FIG. 3). The engine coolant flowingthrough the circulation paths 33 toward the outlet header 32 is heatedand increased in temperature by the PTC heater 40, joins before theoutlet header 32, and flows into the communication opening 52 of thelower heating-medium circulation box 50 through the circulation opening35.

The engine coolant diverges at the communication opening 52 into theindividual circulation paths 54, flows as indicated by an imaginary lineF in FIG. 8 while being heated and increased in temperature again by thePTC heater 40, makes a U-turn at the other end, passes through thecommunication opening 53 and then the circulation opening 36 of theupper heating-medium circulation box 30 and enters the outlet header 32,passes through the outflow portion 37, and flows back to theheating-medium circulating circuit 11. Thus, the engine coolant passingthrough the interior of the heating-medium heating unit 10 flows alongboth surfaces of the PTC heater 40 and circulates in the heating-mediumcirculating circuit 11 while being heated by the heat from the PTCheater 40, so that the temperature of the vehicle interior iscontrolled.

Since the PTC devices 41 a, 41 b, and 41 c that constitute the PTCheater 40 are configured such that the ON/OFF states can be individuallycontrolled by the control circuits incorporated in the control board 22,the individual PTC devices 41 a, 41 b, and 41 c are independently turnedON and OFF by the control board 22 according to the difference betweenthe actual temperature of the engine coolant flowing into theheating-medium heating unit 10 and a necessary temperature (targettemperature), and thus the heating capability is controlled. This allowsthe engine coolant to flow out while being heated and increased to apredetermined temperature.

Next, the relevant part of the present invention will be described. Asshown in FIG. 4, the heating-medium heating unit 10 has a plurality ofjoining surfaces M1 to M4. Joining surfaces between the firstheating-medium circulation box A and the second heating-mediumcirculation box B, that is, a joining surface M1 between the upperheating-medium circulation box 30 and the lower heating-mediumcirculation box 50, joining surfaces M2 and M3 between theboard-accommodating box 20 and the cap 21 and the upper heating-mediumcirculation box 30 that constitute the first heating-medium circulationbox A, and a joining surface M4 between the lower heating-mediumcirculation box 50 and the cap 51 that constitute the secondheating-medium circulation box B, are configured to be sealed withliquid gaskets. Examples of the liquid gaskets include a waterproof,heat-resistant silicone sealant that becomes rubbery when it hardens.

Furthermore, the circulation paths 33 that serve as the heating-mediumcirculation passages of the first heating-medium circulation box A andthe circulation paths 54 that serve as the heating-medium circulationpassages of the second heating-medium circulation box B are providedwith joining-surface cooling channels C1 and C2, respectively. Thesejoining-surface cooling channels C1 and C2 are provided to particularlycool, of the joining surfaces M1 to M4 sealed by the liquid gaskets, thevicinity of the joining surface M1, on which a considerable amount ofthe heat from the PTC heater 40 acts, thereby preventing the liquidgasket applied to the joining surface M1 from being degraded due to theheat.

The joining-surface cooling channel C1 constitutes, of the plurality ofcirculation paths 33, one or two circulation paths close to the joiningsurface M1, and the joining-surface cooling channel C2 constitutes, ofthe plurality of circulation paths 54, one or two circulation pathsclose to the joining surface M1. These joining-surface cooling channelsC1 and C2 are provided at positions closer to the joining surface M1than to the edge of the PTC heater 40. Therefore, the heat from the PTCheater 40 is subjected to heat exchange by the engine coolant that flowsthrough the joining-surface cooling channels C1 and C2 before beingtransmitted to the joining surface M1, which makes the heat difficult tobe transmitted to the joining surface M1. Accordingly, this allows theliquid gasket that seals the joining surface M1 to be protected from theheat, thus enhancing the durability, which prevents the heating mediumfrom leaking through the joining surface M1.

Of the joining surfaces M1 to M4, the joining surface M3 between thelower surface of the board-accommodating box 20 and the upper surface ofthe upper heating-medium circulation box 30, through which the wiringmembers 40 b of the PTC heater 40 pass, includes an outside sealingsection M3 a that seals a space between the heating-medium circulationpassages (circulation paths 33) and the outside and a board sealingsection M3 b that seals a space between the heating-medium circulationpassages (circulation paths 33) and the wire routing holes 28, which areportions communicating with the board-accommodating space S, as shown inFIG. 6, which illustrates the shape of the lower surface of theboard-accommodating box 20. The width W2 of the board sealing section M3b is set to be larger than the width W1 of the outside sealing sectionM3 a. For example, W1 is set at 5 mm, and W2 is set at 8 mm.

As shown in FIG. 4, either one of the upper and lower surfaces of theindividual joining surfaces M1 to M4 are each provided with alevel-difference portion Mc along the inner peripheral edge thereof.Forming the level-difference portions Mc allows the liquid gasket to bemaintained at a predetermined thickness by the level-difference portionMc and to be able to harden without being subjected to a pressing force.If both surfaces of the individual joining surfaces M1 to M4 were madeflat without the flat level-difference portion Mc, the liquid gasketsapplied therebetween would be completely pushed out from the range ofthe joining surfaces when a pressing force is applied thereto, thusposing a worry that sufficient sealability would not be maintained. Theheight of the level-difference portion Mc may be about 0.5 mm to 2.0 mm.

As shown in FIGS. 3, 4, and 8, for example, in the lower heating-mediumcirculation box 50 constituting the second heating-medium circulationbox B, the radiating surface 56 in close contact with the PTC heater 40and the joining surface M1 between it and the first heating-mediumcirculation box A are formed as a continuous flat surface without alevel-difference.

The heating-medium heating unit 10 according to this embodiment isconfigured as described above. This heating-medium heating unit 10provides the following advantages.

First, since the joining surfaces M1 to M4 between the box components20, 21, 30, 50, and 51 that constitute the first heating-mediumcirculation box A and the second heating-medium circulation box B areconfigured to be sealed with the liquid gaskets, the O-rings that areconventionally interposed between the joining surfaces M1 to M4 can beeliminated. This can reduce the number of components and the number ofman-hours for assembling the heating-medium heating unit 10, andmoreover, can eliminate fitting grooves that are conventionally carvedin the individual joining surfaces M1 to M4 to fit the O-rings therein,thereby reducing the number of man-hours for machining the boxcomponents 20, 21, 30, 50, and 51, thus allowing the manufacturing costof the heating-medium circulation box 10 to be remarkably reduced.

Since the joining-surface cooling channels C1 and C2 are provided in theheating-medium circulation passages (circulation paths 33 and 54) of thefirst heating-medium circulation box A and the second heating-mediumcirculation box B, of the four joining surfaces M1 to M4 sealed with theliquid gaskets, the joining surface M1 on which a considerable amount ofthe heat from the PTC heater 40 acts can be cooled favorably. This cantherefore prevent the liquid gasket applied to the joining surface M1from being degraded due to heat, and realizes a sealing technique onlywith the liquid gasket without using an O-ring, thus significantlycontributing to a reduction in the manufacturing cost of theheating-medium heating unit 10.

Furthermore, since these joining-surface cooling channels C1 and C2 areprovided at positions closer to the joining surface M1 than to the edgeof the PTC heater 40, the liquid gasket applied to the joining surfaceM1 can be more reliably protected from the heat from the PTC heater 40.For the joining surfaces M3 and M4, since the positions of thecirculation paths 33 and 54 are closer to the joining surfaces M3 and M4than to the PTC heater 40, it is difficult for the joining surfaces M3and M4 to be affected by the heat from the PTC heater 40.

The shapes of the joining-surface cooling channels C1 and C2 are notlimited to those of this embodiment; they may be other shapes. Forexample, in this embodiment, although the depths and widths of thejoining-surface cooling channels C1 and C2 are equal to or smaller thanthose of the adjacent circulation paths 33 and 54, the depths and widthsmay be larger than those of the circulation paths 33 and 54 so that muchmore engine coolant will flow through a portion closer to the joiningsurface M1, thereby further enhancing the cooling performance of thejoining surface M1.

Furthermore, in this heating-medium heating unit 10, of the joiningsurfaces M1 to M4, the joining surface M3 through which the wiringmembers 40 b of the PTC heater 40 pass is configured such that the widthW2 of the board sealing section M3 b is set to be larger than the widthW1 of the outside sealing section Mia; therefore, while the O-ring onthe joining surface M3 is eliminated so that the manufacturing cost canbe reduced, coolant leakage to the board-accommodating space S in whichthe control board 22 is accommodated can be reliably prevented, andhence the reliability of the heating-medium heating unit 10 can beenhanced.

Furthermore, in this heating-medium heating unit 10, since the radiatingsurface 56 of the lower heating-medium circulation box 50 thatconstitutes the second heating-medium circulation box B and the joiningsurface M1 to the first heating-medium circulation box A are formed as acontinuous flat surface without a level-difference, the upper surface ofthe lower heating-medium circulation box 50 can be made completely flat,thereby remarkably facilitating processing of the lower heating-mediumcirculation box 50, thus reducing the manufacturing cost of theheating-medium circulation box 10.

Furthermore, in this heating-medium heating unit 10, since the PTCheater 40, the first heating-medium circulation box A, and the secondheating-medium circulation box B are formed in a rectangular shape, andthe wiring members 40 b of the PTC heater 40 are extended together fromthe end of the PTC heater 40 in the longitudinal direction, the wiringmembers of the PTC heater 40 are not interposed between the long side ofthe PTC heater 40 and the long side of the heating-medium circulationbox 10 as in the related art. Therefore, the outer peripheral dimensionsof the heating-medium circulation box 10 can be brought close to theplanar outside dimensions of the PTC heater 40, and the width dimensionof the heating-medium circulation box 10 can be reduced, and thus themanufacturing cost can be reduced.

Furthermore, in this heating-medium heating unit 10, since the PTCdevices 41 a, 41 b, and 41 c that constitute the PTC heater 40 aredisposed in a plurality of rows along the channel direction of theheating-medium circulation passages (circulation paths 33 and 54), theplurality of PTC devices 41 a, 41 b, and 41 c have different widths, andthe ON/OFF states of the PTC devices 41 a, 41 b, and 41 c can beindividually controlled, the wiring members 40 b can be easily providedtogether at one end of the PTC devices 41 a, 41 b, and 41 c in thelongitudinal direction, the quantity of heat from the PTC heater 40 canbe controlled with a simple configuration, and thus a reduction in themanufacturing cost due to the size reduction of the heating-mediumheating unit 10 and enhanced reliability can be achieved.

Furthermore, since the vehicle air conditioner 1 according to thepresent invention is provided with the blower 4 that circulates outsideair or vehicle interior air, the cooler 5 provided downstream of theblower 4, and the radiator 6 provided downstream of the cooler 5 and isconfigured to circulate engine coolant heated by the heating-mediumheating unit 10 according to the present invention through the radiator6, the reliability of the heating-medium heating unit 10 can beenhanced, and furthermore, the reliability of the entire vehicle airconditioner 1 can be enhanced while achieving miniaturization of theheating-medium heating unit 10 and a reduction in the manufacturingcost.

Although this embodiment has been described as applied to an example inwhich the heating-medium heating unit is used in a vehicle airconditioner, the heating-medium heating unit according to the presentinvention may be applied to air conditioners that are not designed forvehicles, heaters, refrigerators and so on.

REFERENCE SIGNS LIST

-   1 vehicle air conditioner-   4 blower-   5 cooler-   6 radiator-   10 heating-medium heating unit-   20 board-accommodating box serving as box component-   21 cap serving as box component-   22 control board for controlling PTC heater-   28 wire insertion hole serving as portion communicating with    board-accommodating space-   30 upper heating-medium circulation box serving as box component-   33 circulation path serving as heating-medium circulation passage-   38 radiating surface PTC heater-   40 b wiring member of PTC heater-   41 a, 41 b, 41 c PTC device-   50 lower heating-medium circulation box serving as box component-   51 cap serving as box component-   54 circulation path serving as heating-medium circulation passage-   56 radiating surface-   A first heating-medium circulation box-   B second heating-medium circulation box-   C1, C2 joining-surface cooling channel-   M1 to M4 joining surface-   M3 a outside sealing section-   M3 b board sealing section-   S board-accommodating space-   W1 width of outside sealing section-   W2 width of board sealing section

1. A heating-medium heating unit, comprising: a flat PTC heater; a firstheating-medium circulation box in which a plurality of box componentsare stacked one on another, which is in close contact with one surfaceof the PTC heater, and in which a heating-medium circulation passage isformed in the interior; and a second heating-medium circulation box inwhich a plurality of box components are similarly stacked on oneanother, which is in close contact with the other surface of the PTCheater, in which a heating-medium circulation passage is formed in theinterior, and which is joined to the first heating-medium circulationbox in a liquidtight manner, wherein a heating medium that circulatesthrough the heating-medium circulation passages in the first and secondheating-medium circulation boxes is heated by heat radiated from bothsurfaces of the PTC heater, wherein PTC modules that constitute the PTCheater are disposed in a plurality of rows along the channel directionof the heating-medium circulation passages, the plurality of PTC moduleshave different widths, and ON/OFF states of the PTC modules can beindividually controlled.
 2. A vehicle air conditioner including a blowerthat circulates outside air or vehicle interior air, a cooler provideddownstream of the blower, and a radiator provided downstream of thecooler, wherein a heating medium heated by the heating-medium heatingunit according to claim 1 can circulate through the radiator.